The present invention relates to a down-the-hole drill (“DHD”) hammer. In particular, the present invention relates to a DHD hammer having a sliding exhaust check valve assembly and more particularly, a sliding exhaust check valve assembly that combines supply and exhaust check valves into a single unit operation.
Typical DHD hammers utilize what is known as “reactive” seals for sealing the DHD hammer's interior from its exterior environment, such as water and debris. The seals are known as “reactive” seals because they require the movement of exhaust flow to displace or open flow passageways within the DHD hammer. However, such DHD hammers also require that exhaust pressures be minimized for proper functioning of the DHD hammer. As such, the level of reactive forces/pressures for the “reactive” seals were also minimized, thereby potentially negatively impacting the “reactive” seal's effectiveness.
A DHD hammer, such as the present invention, having a sliding exhaust check valve addresses the foregoing limitations of reactive seals.